The present invention relates to a golf ball having a core and cover of one or more layer. More specifically, the invention relates to a golf ball which has both a good feel on impact and excellent scuff resistance while retaining a good flight performance.
Ionomer resins have been widely used of late in golf ball cover materials. Ionomer resins are ionic copolymers of an olefin such as ethylene with an unsaturated carboxylic acid such as acrylic acid, methacrylic acid or maleic acid, in which some of the acidic groups are neutralized with metal ions such as sodium, lithium, zinc or magnesium. In particular, ionomer resins have excellent characteristics such as durability and rebound resilience, and are thus well-suited for use as the base resin in golf ball cover materials.
Ionomer resins account for most of the cover material resin in use today, and enable the production of golf balls endowed with the above properties. Yet, golfers are always on the lookout for golf balls having a high rebound resilience and excellent flight characteristics. Examples of such improvements include the admixture of a third component such as an alkyl acrylate in the base resin for a core material, as described in U.S. Pat. No. 6,653,382 and U.S. Pat. No. 6,777,472. However, given that the oleic acid included in these base resins is an unsaturated fatty acid, such base resins are difficult to use as a cover material because they readily oxidize and undergo increased discoloration under heating. In addition, the inclusion of oleic acid lowers the hardness of the base resin, making it very difficult to adjust the hardness of the base resin to a value that is suitable for a cover material.
Given the importance placed on the feel of the ball when played, the use of a low-hardness ionomer in the cover material has also been proposed. However, the use of a low-hardness ionomer may lower the initial velocity of the ball and reduce the scuff resistance.